Liquid fuel pumping apparatus



May 27, 1969 p GL|K|N ET AL 3,446,148

LIQUID FUEL PUMPING APPARATUS Filed May 23, 1967 United States Patent 3,446,148 LIQUID FUEL PUMPING APPARATUS Paul Edgar Glikin, London, and Keith Finer Hutcheon, Gerrards Cross, England, assignors to C.A.V. Limited, London, England, a British company Filed May 23, 1967, Ser. No. 640,616 Claims priority, application Great Britain, May 31, 1966, 24,085/ 66 Int. Cl. F04!) 13/00 US. Cl. 1032 3 Claims ABSTRACT OF THE DISCLOSURE Liquid fuel pumping apparatus comprising a pumping plunger reciprocable in a bore formed in a rotary distributor, the distributor having a delivery passage for registration with an outlet port, the cam lobe being so shaped that after an injection stroke and after communication of the delivery passage with an outlet port has been broken, the plunger is allowed to move a predetermined extent in the direction in which it moves during a filling stroke.

This invention relates to liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and of the kind comprising an injection pump including a cam and a pumping plunger, relative movement being arranged to occur between the cam and the plunger in timed relationship with the engine so that the injection pump partakes of alternate filling and injection strokes, a distributor member arranged to be driven in timed relationship with the engine, the distributor member having a delivery passage through which fuel flows from the injection pump during a delivery stroke and which is arranged to communicate in turn and as the distributor moves with a plurality of outlet ports which are formed in a body part, the distributor also being provided with an inlet passage which as the distributor moves opens to an inlet port to allow fuel to flow to the injection pump during a filling stroke thereof.

The object of the present invention is to provide such an apparatus in a simple and convenient form.

According to the invention an apparatus of the kind specified is characterised in that the cam is so shaped that after an injection stroke and after communication of the delivery passage with an outlet port has been broken and before the inlet passage opens to the inlet port, the plunger is allowed to move a predetermined extent in the direction in which it moves during a filling stroke, the plunger then being held against movement in said direction for a short period before being allowed to move its fullest extent.

In the accompanying drawings:

FIGURE 1 is a sectional side elevation of one example of a pumping apparatus to which the invention may be applied,

FIGURE 2 is a section on the line 2-2 of FIGURE 1,

FIGURE 3 is a side elevation of a part which can be incorporated in the apparatus of FIGURES l and 2,

FIGURE 4 is a developed view to an enlarged scale of the profile of a cam lobe of the apparatus of FIGURES 1 and 2, and

FIGURE 5 is a View similar to FIGURE 4 of a cam lobe for the apparatus when the part shown in FIGURE 3 is incorporated.

The example of a liquid fuel pumping apparatus illustrated is for supplying fuel to a four cylinder compression ignition engine and there is provided a body part in which is mounted a rotary cylindrical distributor 11 which is adapted to be driven in timed relationship with the engine with which the apparatus is associated. At one 3,446,148 Patented May 27, 1969 end of the distributor is formed a transversely extending bore '12 in opposite ends of which are slidably accommodated a pair of pumping plungers '13. The plungers are adapted to be moved inwardly as the distributor rotates by the interaction of rollers 14 disposed at the outer ends of the plungers respectively, with two pairs of diametrically disposed cam lobes 15 formed on the internal periphery of an annular cam ring 16 mounted in the body and surrounding the distributor at this point.

At the other end of the distributor is mounted the rotary part of a vane type feed pump 17 having an outlet 18 formed within the body part and an inlet 19 for com munication with a source of fuel. The inlet and outlet of the feed pump are interconnected by way of a relief valve 20 which acts to control the output pressure of the feed pump.

Formed in the distributor is a longitudinal passage 21 which at one end is in communication with the transversely extending bore 12. At another point the longitudinal passage is in communication with a radially disposed delivery passage 22 also formed in the distributor, and which is arranged to register in turn and as the distributor rotates, with four equi-angularly spaced delivery ports 23 formed in the body part and in communication respectively with four outlet ports. In use, the outlet ports are connected by way of pipe lines respectively to the injection nozzles (not shown) of the engine. At another point the longitudinal passage is in communication with four equi-angularly spaced and radially disposed inlet passages 24, which are arranged to register in turn and as the distributor rotates with an inlet port 25 formed in the body part. 'Ihe inlet port is in communication with the outlet 18 of the feed pump by way of passages within the body part, and for controlling the flow of fuel through the inlet port a throttle valve 26 is provided, the setting of which is in part dependent upon a governor which is sensitive to the speed at which the engine is operating. The communication between the delivery passage 22 and a delivery port 23 is arranged to occur when the plungers are moved inwardly by the cam lobes 15 and the registration of an inlet passage 24 with the inlet port 25 is arranged to occur during strokes.

The profile of one of the cam lobes is shown in FIG- URE 4 of the accompanying drawing, it being appreciated that each cam lobe is identical. As viewed in the drawing, after a delivery port has opened (point A on the diagram) the roller 14 will be moved upwardly as relative movement occurs between the roller and the cam lobe. During this upward movement of the roller inward movement is imparted to the plungers and fuel will be delivered to the delivery passage 22 and will flow through the appropriate outlet port to an engine cylinder. When the roller reaches the crest of the cam lobe further delivery of fuel to the engine will cease. The cam is so shaped however, that the roller is permited to move downwardly a predetermined amount after which it is held stationary until the delivery port closes (point B on the diagram). The purpose of this downward or outward movement of the plungers 13 is to relieve the pressure in the pipe line connecting the appropriate outlet port and injection nozzle together with the passage in the pump which connects the delivery and outlet port. Referring again to the drawing after the delivery part has closed, the roller is permitted to move downwardly a further amount after which it is again held stationary for a short period. The purpose of this movement is to relieve the fuel pressure remaining in the passages of the distributor, and the purpose of the second stationary period is to arrest the motion of the roller and plunger which occurs during this process. After the second stationary period the cam is shaped so as to the interval between successive injection permit the roller to move downwardly its full extent. The inlet port 25 is opened to an inlet passage 24 at point C and plungers will be moved outwardly positively by the action of fuel entering the transversely disposed bore.

In an alternative arrangement unloading delivery valves as shown in FIGURE 3 are provided intermediate the delivery ports 23 and the associated outlets. Each valve comprises a body which at its lower end is provided with flutes 30 for guiding the axial movement of the body within a bore 41 which forms part of the passage interconnecting the delivery part and its associated outlet. The upper portion of the body is of truncated conical form and defines a closure element which co-operates with a seating 42 defined about the bore 41. The body is loaded by a coiled compression spring 43 so that the closure element is urged into contact with the seating. Moreover, intermediate the closure element and the fluted port-ion of the body is a plain cylindrical collar 44.

In use, fuel flowing through the bore 41 towards the outlet moves the body against the action of the spring until fuel can flow past the collar to the outlet. When the flow of fuel ceases the spring urges the body in the reverse direction and in so doing a predetermined quantity of fuel is returned to the transversely disposed bore 12 before the upper portion of the body contacts the seating 42. The cam profile for use with this arrangement is seen in FIGURE 5 and it will be seen that the delivery port is opened to a delivery passage at point D as in the previous example and the delivery valve will be lifted as fuel flows. When injection of fuel ceases the delivery valve will close shortly after the crest of the cam has been passed. The point of closure is indicated at E and as soon as the valve is closed communication of the delivery passage and outlet port is broken. The plungers are then permitted further outward movement during which time the pressure within the passages of the pump is relieved and then follows a short dwell period during which the plungers are held at rest. Subsequently the inlet port 24 is opened at point P but before this the delivery passage 22 is closed to an outlet. It should be noted that in this example the point G at which the delivery passage 22 is closed can occur any time between points E and F since the aforesaid communication is broken by the delivery valve.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and comprising a cam, a pumping plunger, the cam having a plurality of lobes whereby as the cam and plunger are driven relative to each other in timed relationship with an associated en gine, inward pumping movement will be imparted to the plunger, the cam and plunger constituting an injection pump, the apparatus further comprising a distributor member rotatably mounted in a body part of the apparatus and arranged to be driven in timed relationship wtih an associated engine, a delivery passage formed in the distributor member, a plurality of outlet ports formed in the body part, said outlet ports in use, being connected respectively to injection nozzles mounted on the associated engine, the delivery passage being placed in communication with said outlet ports in turn to permit fuel to flow from the injection pump to the outlet ports, and valve means disposed intermediate the delivery passage and each outlet port, the valve means serving to close the communication between the delivery passage and outlet ports after delivery of fuel by the injection pump has finished, each cam lobe having an inclined forward faceand a declined rearward face, a first dwell portion on the rearward face of each cam lobe and positioned to arrest temporarily the outward movement of the plunger after said valve means has closed communication between the delivery passage and outlet port.

2. A liquid fuel pumping apparatus according to claim 1 in which the outlet ports communicate with delivery ports respectively opening onto the periphery of the distributor member at; positions to register with the delivery passage thereby to constitute said valve means, the declined rearward faces of the cam lobes having second dwell portions to temporarily arrest the outward movement of the plunger before closure of the valve means, said first and second dwell portions being spaced by an amount sufficient to ensure relief of pressure within the passages in the apparatus.

3. A liquid fuel pumping apparatus according to claim 1 in which the outlet ports communicate with delivery ports respectively opening onto the periphery of the distributor member at positions to register with the delivery passage, said valve means being positioned intermediate the delivery ports and outlet ports and being arranged to close at the end of the delivery of fuel by the injection pump.

References Cited UNITED STATES PATENTS 2,946,292 7/ 19 Chmielecki 103160 2,961,004 11/ 1960 Aldinger et a1.

3,292,546 12/1966 Evans l032 3,363,568 1/1968 Evans 123139 X DONLEY J. STOCKING, Primary Examiner.

LEONARD H. GERIN, Assistant Examiner.

US. Cl. KR. 123-139 

